The prior art includes a variety of constant rate flow controllers employing elastomeric elements that are deformable in proportion to the applied pressure to vary the area of a flow passage. Such devices are found, for example, in faucet spouts, drinking fountains, showerheads, shower arms, automatic washing machines and agricultural drip irrigators and each of these applications may have a relatively broad range of flow rate requirements. The flow rate of a given device depends on a number of factors including the geometry and modulus of elasticity of the elastomeric element and the geometry of the members cooperating with the elastomeric element. Thus, in many prior art devices the properties of the elastomeric element and of the cooperating members must be tailored to provide a particular flow rate. This results in increased manufacturing costs due to the need, for example, for a multiplicity of mold cavities of different geometries.
As dwelling construction and plumbing materials become lighter, an emerging problem that has not been satisfactorily solved by the prior art is that of excessive noise generated by flow control devices, particularly at high flow rates and pressures. Illustrative of the attempts to meet this problem are U.S. Pat. Nos. 3,630,455 and 3,642,031. The device of U.S. Pat. No. 3,630,455, however, employs an elastomeric flow disk having projections that are in frictional engagement with a perforated plate. As a result, these projections tend to wear rapidly thereby altering the flow rate of the device. The insertion of a noise-reducing fibrous plug in the flow path, as suggested in U.S. Pat. No. 3,642,031, causes clogging as well as eventual hardening of the plug caused by interaction with the minerals carried by the water.
Moreover, many flow control devices of the prior art tend to be complex and costly. In some cases, as illustrated by U.S. Pat. No. 2,878,836 (Binks), the flow control element comprises a multiple-part structure that must be assembled before incorporation into the housing of the flow control device. High material cost is also a factor in those devices employing relatively large elastomeric elements.
Furthermore, many of the flow control devices of the prior art cannot be used in conjunction with laminar stream devices (such as that disclosed in U.S. Pat. No. 4,119,276 (Nelson)) because the characteristics of the water flow discharged from the flow control device is not compatible therewith.
In view of the foregoing, an overall object of the present invention is to provide an improved flow control device of the type incorporating an elastomeric element and which is capable of accurately controlling flow rates in a variety of plumbing system environments.
Another object of the invention is to provide a flow control device in which a single elastomeric element of preselected geometric and material properties that cooperates with a member having a single basic design may be used to provide a broad range of flow rates.
Still another object of the invention is to provide a flow control device that is extremely quiet in operation across a wide range of pressures and flow rates.
A further object of the invention is the provision of a flow control device that is simple, economical and easy to maintain.
Yet another object of the invention is to provide a flow control device employing an elastomeric element that is not subject to wear and therefore has a long life.
A still further object of the invention is to provide an improved flow control device that is compatible with the production of a laminar stream from a faucet spout.